In recent years, the data recording density of magnetic disk devices has been remarkably enhanced, and its annual increase rate is said to be some 150%. According to this remarkable increase in the data recording density, the recording capacity of the magnetic disk devices is drastically enhanced. The increase in the data recording capacity promotes size reduction of the magnetic disk devices, and there are being practically used disk devices with high cost effect, such as one disclosed in Japanese Published Patent Application No. Hei. 8-249127, which replace semiconductor memories of various electronic devices such as cameras, facsimiles, portable phones, modems, beepers, hand-held computing equipments, printers, and copy machines.
A current magnetic device is provided with a rotation-type actuator like a tone arm of a record player, so as to obtain a high access rate. A slider is attached to the end of an actuator arm. The surface of the slider that is opposed to a disk medium is an air bearing surface. The slider draws an airflow generated by rotation of the disk medium between the air bearing surface and the surface of the disk medium, whereby the slider flies from the disk medium. That is, the slider forms and maintains a self-pressure-type air bearing film between the slider and the disk medium storage surface. Accordingly, the flying altitude of the slider with respect to the surface of the disk medium, that is, a distance between the disk medium surface and the slider, is equivalent to the thickness of the air bearing film. Due to this film, less mechanical contact is caused between the slider and the disk medium during the rotation of the disk medium, thereby suppressing friction and wear.
The slider has a magnetic head for writing data on the disk medium or reading the data from the disk medium, inside. The magnetic head is generally arranged in the vicinity of the air efflux end on the air bearing surface of the slider that is opposed to the disk medium.
Since the rotation-type actuator is used as described above, directions of movement between the slider and the disk medium and the airflow under the slider are no longer uniform, and they have various angles with respect to the ordinate of the slider (an axis supposed to pass in the center of the slider in the direction of a long side of the slider or the actuator). Further, a high-speed searching operation of the accessing actuator causes the direction of the movement between the slider and the disk medium and the direction of the airflow under the slider to be inclined with respect to the ordinate. Thus, in a recent magnetic disk device having the rotation-type actuator, the movement direction is no longer equal to the ordinate direction from the front of the slider to the back thereof, or the direction slightly deviated from the ordinate direction.
Here, an angle formed by the disk medium movement direction with the ordinate of the slider is referred to as a skew angle. When the actuator arm is located at the outside end of the disk medium or outside thereof, the skew angle is positive. When the actuator arm is located so that the movement direction corresponds to the inside end of the disk medium or the hub thereof, the skew angle is negative.
In the magnetic disk device, a flying height of the slider with respect to the disk medium at recording/reproduction tends to be decreased with an increase in the recording density. This decrease in the flying height is achieved by a so-called negative-pressure-use-type slider as disclosed in Japanese Patents No. 1505878, No. 2778518, No. 2803639, and the like, in which the air bearing surface of the slider is formed by plural approximately plane surfaces of different heights. Positive pressure (pressure acting in the direction in which the slider gets far from the disk medium) is generated on the approximately plane surfaces which are formed high so as to narrow a gap between the slider and the disk medium, while negative pressure (pressure acting in the direction in which the slider gets near to the disk medium) is generated on the approximately plane surfaces which are formed low so as to enlarge the gap between the slider and the disk medium, and the positive pressure and the negative pressure are balanced, thereby making the slider fly.
As described above, when data access is performed in the magnetic disk device, the slider moves in a range from the inner circumference of the disk medium to the outer circumference thereof, and, at this time, a flying height and posture of the slider are varied. This is because, in the magnetic disk device having the rotation-type actuator, not only a relative velocity between the slider and the disk medium but also the skew angle are varied according to a radius position on the disk medium, so that a distribution of air pressure generated on the air bearing surface is varied. The variation of the slider flying height deteriorates electromagnetic conversion efficiency of the magnetic head. Particularly, in a magnetic disk device requiring high recording density, the flying height at a position of the magnetic head is required to be uniform from the inner circumference of the disk medium to the outer circumference thereof and, further, stricter restrictions are placed on the flying height variation with reduction in the slider flying height.
Further, when the slider is required to fly at a predetermined height at the above-described magnetic head position, the variation of the slider flying posture, particularly the variation of a roll angle in the direction of the slider abscissa, causes reduction of the flying height at a position of the minimum flying height and, thus, brings the slider and the disk medium into contact, resulting in a risk of inducing so-called head crush.
In a magnetic disk device currently under development that employs a disk medium of minor diameter such as 27 mm, a relative velocity between the slider and the disk medium differs greatly from that in a magnetic disk device employing a disk medium of, for example, 95 mm or 84 mm in diameter. Thus, sufficient flying force cannot be obtained from airflow and, therefore, it is further difficult to maintain a predetermined flying height and a uniform flying posture. This becomes a major concern in developing small-size magnetic disk devices.
The present invention is made to solve the above-mentioned problems and has for its object to provide a slider which can maintain a uniform flying posture and a predetermined flying height by suppressing variations of the roll angle and the flying height of the slider, and a disk device employing this slider.